SURG-29. CAN NEOADJUVANT CHEMOTHERAPY INCREASE EXTENT OF RESECTION IN DIFFUSE LOWER-GRADE GLIOMA?

Abstract

Abstract INTRODUCTION Maximal safe surgical resection remains front-line treatment for diffuse lower-grade gliomas (DLGGs). Greater extent of resection (EOR) can delay transformation, control seizures, and improve survival. EOR is limited by the infiltrative nature of DLGGs and eloquent brain location preponderance. We investigated the role of neoadjuvant chemotherapy in tumour volume reduction (TVR) for cases in which a meaningful EOR was deemed unachievable. METHODS Retrospective review (2000-2020) of patients in a large tertiary UK brain tumor centre who serendipitously underwent management that did or could mimic a neoadjuvant chemotherapy pathway. Inclusion criteria: >18 years at diagnosis; histologically-proven WHO grade 2 supratentorial glioma; received chemotherapy alone after biopsy then +/- debulking. Tumour volume delta +/- EOR were calculated on serial MRI T2/FLAIR sequences using a semi-automated quantitative analysis tool (Smartbrush, BrainLab® AG). RESULTS Group 1 (neoadjuvant chemotherapy and then surgery, n=4): debulking was considered unachievable initially but then possible post-chemotherapy. Median TVR post-chemotherapy was 16.90% (range 0.45–64.90%). Mean EOR was 68.67% (33.72–100%). Median overall survival (OS) and progression free survival (PFS) were 85 (18–154) and 62 (13–153) months, respectively. Group 2 (biopsy followed by chemotherapy alone, n=7): debulking was considered unachievable initially. Median TVR post-chemotherapy was 25.68% (-294.95–46.02%, one patient progressed during chemotherapy). Median OS and PFS were 92 (6–135) and 27 (3–80) months, respectively. On re-review, and based on Group 1 results, some Group 2 patients may have been able to undergo debulking with meaningful EOR post-chemotherapy. CONCLUSIONS Chemotherapy can have a significant impact on reducing tumour volumes, such that cases initially deemed unsuitable for debulking may be converted into those in which a meaningful EOR can be achieved. Larger, multicentre, retrospective studies, and prospective trials are needed to determine the role of chemotherapy as a neoadjuvant tool in the management of DLGGs.